Toyota Repair: The headlights of my Toyota,..., heater fan, best guess

Question
The headlights of my Toyota, flicker (or dim) fast while I am driving.  The same thing happens with the lights on the dashboard, they go bright & lighter very fast.  The heater fan the same thing.  The sound tells me it is also changing speeds.

But if I come to a complete STOP, the flickering/ dimming "usually" stops.  But a few times the heater fan which was on fast, slows right down (not a complete stop) when I pull up to a stop sign & will only start FAST again when the car is going at normal speed.

The radio signal does not flicker & is normal.

Can you help?  BIG thanks.

Answer
Hello Dewey and welcome to my expert page,
Very strange problem, my best guess is that there may be a wiring problem or a fuse connection that is loose, let me know what year and model it is, I need to look at a wiring diagram to see where the problem may be.